1. Field of the Invention
The invention relates to a contact arrangement for a change-over contact relay having a movable contact spring which bears at its free end a switching contact piece on each side and has a recess in the region of the switching contact pieces, a stranded conductor-shaped connecting line being connected directly in an electrically conducting manner to at least one of the contact pieces.
2. DESCRIPTION OF THE RELATED ART
In a known contact arrangement as shown in European Application (01 67 688) of this kind for a change-over contact relay of high switching capacity, a contact spring which can be moved between two corresponding contact elements is provided at its free end with two switching contact pieces arranged on both sides. The first switching contact piece arranged on the one side of the movable contact spring is connected directly to an electrical connecting line constructed as a stranded copper conductor so that the contact spring itself does not conduct the current to be switched. In order to provide a contacting face which is sufficient for the connection of the electrical connecting line to the first switching contact piece, the latter is made so long that it projects beyond the width of the free end of the movable contact spring. The second switching contact piece arranged on the other side of the free end of the contact spring corresponds in its width approximately to the width of the free end of the contact spring. In the known contact arrangement, this comparatively short switching contact piece is either soldered to the contact spring or connected by means of an extension piece to the first comparatively long switching contact piece. In both variants, the current to be switched flows in each contact-making position of the contact spring via the long switching contact piece so that the latter experiences a greater degree of heating in comparison with the short switching contact piece. If the current to be switched flows to the short switching contact piece, it has to pass at least two connections. However, each connection constitutes an increased ohmic resistance which causes an electrical loss power. The differently constructed switching contact pieces give rise to a nonsymmetrical mass distribution which is manifested in particular in an unfavorable dynamic behavior during the switching processes, for example in an increased inclination to bouncing. Due to the long switching contact piece, the known contact arrangement requires a substantially higher amount of noble metal in comparison with the amount of noble metal required for the pure contact-making faces of the switching contact pieces. Furthermore, the manufacture and processing of switching contact pieces of different lengths increases the manufacturing costs for the known contact arrangement.
German application 1 6651958 discloses a contact arrangement in which a contact spring bears a contact piece on both sides. A further U-shaped leaf spring serves here as a connection for the current supply so that double the thickness of the leaf spring exists in the region of the contact pieces. However, this leaf spring for the current supply exerts additional forces on the contact spring; for this reason, it is also limited in cross-section and thus cannot conduct currents of any desired strength. Because of its leaf spring shape, it cannot be bent into any desired direction either, and is thus only to be used for quite specific contact spring arrangements. British application 1 158 119 shows a contact spring arrangement with contact pieces mounted on both sides, which pieces are soldered to one another through a hole in the contact spring. However, a separate current supply is not provided in this publication.